Heat controlled switch



Aug. 2, 1949. J, MESH 2,478,117

HEAT CONTROLLED SWITCH Filed Feb. 13, 1946 INV ENTOR 77/501703: J[1131/1 ATTOR EYS v I A 2,478,117 'UNlTED STATES PATENT OFFlCE HEATCONTROLLED SWITCH Theodore J. Mesh, Easthampton, Mass., asslgnor toGilbert & Barker Manufacturing Company, West Springfield, Mass., acorporation of Massachusetts Application February is, 1946, Serial No.647,277

Patented Aug. 2, 1949 4 Claims. 1

This invention relates to an improved form of heat controlled switch. Itmay be used as a thermostat, a flame detector, a time switch, and forother specific switch uses. In these specific uses thenew switch iscompetitive with many known forms of automatic switches. One idea of theimprovement is to provide a new switch and mode of operation for agenerally old result, 1. e. an automatic switching operation under heatcontrol. Some advantages of the new structure and mode of operation arein its simplicity, its rugged character, its economy of manufacture, andits adaptability for use under circumstances where known heat controlledswitches are not so useful for one reason or another.

For example the so-called electric-eye or photo-electric switch deviceis sometimes employed as a flame detector. The theory of such anapplication is good but the practice has some objections. In oil burnerwork the plan is to have an electric eye shut off the burner when theflame is not detected within a predetermined time interval after theburner starts. This is then an emergency switch operation to avoidfeeding oil in the absence of a flame to consume it. As is well known,the electric eye and more particularly the electronic tube generallyused in conjunction with it both have an uncertain limited life and aresubject to breakage, burnout, and other causes of failure. In any event,they require periodic replacement. Every such failure renders the burnerinoperative, requiring the services of a repairman, subjecting the userto the periodic failure of his heating plant.

An example of the utility in the present invention will be seen bycomparing its operation with the electric eye operation. The new switchwill have the convenience of electric eye operation but without nearlyas much liability of failure. The new device may be delicately adjustedfor sensitive operation, but there is nothing delicate about thetangible features of its operation. It is rugged, will not get out oforder, and may be depended upon for more certain operation than theelectric eye device.

The principles of operation and illustrative examples of the newstructure as applied for use will be disclosed with the accompanyingdrawings,

Fig. l is a general form of the switch device;

Fig. 2 is an example of its application as a flame detector in an oilburner;

Fig. 3 is an example similar to Fig. 2 with parts in a differentoperative position; and

Fig. 4 is an example of its application as a time switch.

The drawings are generally diagrammatic to give a disclosure to oneskilled in the art. The finished commercial designs may take many forms.The principles of construction, mode of operation, and results of theinvention will be 2 understood from these drawings and theirexplanation.

In Fig. 1 a switch is shown with its operating means, to disclose theidea and its practice broadly. A stand I, supports a brass cylinder 2,which holds internally a permanent magnet 3 on pivot 4. This magnet hastwo opposed flat polar faces. Magnet 3 is free to swing on its pivot. Anarm 8 carries a contact 9 to work with contact l0. These contacts makeand break a circuit not shown. A cover 5 is screwed onto one end of tube2. It is adjusted to make the gap a between its inside face and theright hand face of magnet 3 a predetermined amount, called gap a. Asimilar cover 6 is screwed into the other end of tube 2 to make asimilar gap between its inside face and the magnet 3, called gap 1). Thecovers 5 and B are preferably mounted in brass holders 5' and 6'. Thesecovers serve as armatures one for each polar face of the magnet.

These covers 5 and 6 are made of a magnetic alloy whose magneticpermeability decreases with.

For example, it may increase in temperature. have a permeability ofabout units at room temperature and decrease about .45 of a unitfor eachdegree Fahrenheit increase in alloytemperature. Such an alloy isavailable on the market, for example from Carpenter Steel Company. Irefer to what the trade calls Temperature Compensator 30, Type 1 as onealloy suitable for my purpose. I understand it is a ferrous alloycontaining about 30% nickel. I prefer to use the alloy in thin sheetform, for example about .030 inch in thickness, for covers 5 and 6. Iwill refer to covers 5 and 6, since the parts are indicated as covers.But I mean to include within the terms "cover or covers such things asplates or diaphragms or the like regardless of their exact structure ormountings.

Magnet 3 may take many forms and may be magnetized in numerous differentways, but it is generally desirable that no additional member benecessary to complete the magnetic circuit or circuits other thandiaphragms as provided by covers 5 and 6 positioned with gaps a and b. Apermanent magnet is very well suited to my purpose and is the kindindicated. Because of the relatively low magnetic permeability of thealloy of covers 5 and 6, it may in some instances be desirable to usemultiple magnets or a plurality of magnets to produce the requiredforces of attraction between magnet 3 and each of the covers 5 and 6.

Cover 6 has an opening to pass bendable arm 8 carrying contact 9. Cap 1on cylinder 2 may be used as a second cover beyond cover 6 to carry andprotect contacts l0 and l l, the latter contact being used in the eventthe circuit wiring makes it useful. No such wiring is shown but ofcourse is implied from the parts shown.

The structure of Fig. 1 may be used in many ways similarto an electriceye" particularly for detecting radiant heat conditions and operating aswitch according to such conditions. The cover 5 faces the directionfrom which radiation is expected. When such radiation or heat wavesstrike cover 5 its temperature will rise and this will cause thecombination to operate.

An example of the operation will be given. Assume that contacts 9 andIII will give the desired circuit before the rise in temperature occursand that contacts 9 and II will give the desired circuit after the risein temperature occurs. Assume that gap a is enough less than gap b thatmagnetic attraction acts to hold gap a as indicated with contacts 9 andI closed. This will be the normal condition of the device with the partsat one temperature. The attraction across gap a will be greater thanthat across gap b and the pressure between contacts 9 and I will be afunction of the difference of these forces.

When cover, or detector plate 5, facing whatever starts to cause a risein temperature, is heated, its magnetic permeability decreases. Thiscauses a drop in magnetic attraction between magnet 3 and its adjacentplate 5. But there is no corresponding drop of attraction between magnet3 and its adjacent cover across gap b. The reason is that cover 5 isheated and cover 6 is not heated under the conditions stated. As thisdrop in the attraction of parts across gap a continues, the attractionacross gap b remains substantially constant. The attraction across gap11 will gradually become less than that across b, whereupon magnet 3will swing on pivit 4 and snap toward cover 5 to open contacts 9 and I0and close contacts 9 and II. This effect is what is wanted when the risein temperature occurs at the right hand part of the structure with cover5 facing the source of radiation or heat as an electric eye device wouldface it. The device is thus seen to respond to difl'erence intemperature of covers 5 and 5, whether caused by radiation or othermeans not shown. 01 course the temperature on all sides may risegradually while that on one side of cover 5 rises faster than on theother side. The effect will not be different on this account.

When the device operates as just described, contacts 9 and I I may bekept together or contacts 9 and It kept apart. The magnetic attractionbetween magnet 3 and plate 6 will then hold the switch in the operatedposition because the ap between will be less than the gap between magnet3 and cover 5 after the operation closes contacts 9 and II. When anautomatic return of the parts to their original position is desired,however, the following arrangement may be made. Covers 5 and 5 and stopelement II are so adjusted that gap at will always be less than gap b.Contacts l0 and l I are indicated as axially adjustable by nuts l0' andII. With this adjustment, and with covers 5 and 5 at the sametemperature, magnet 3 can never reach the balance or neutral positionmidway between them and will snap back toward cover 5 after thetemperature differential is lost between covers 5 and 5. Under theseconditions, if plate 5 be heated as previously described, the switchwill be operated as before stated, except that when temperatureequilibrium is restored, either by permitting 5 to cool olf, oralternately by raising the temperature of 6, magnet 3 will snap backtoward cover 5 thus eiiecting the desired automatic return. The switchcontacts l0 and H as well as plates 5 and 5 are indicated as adjustable.The contacts l0 and II may be made to function conveniently asadjustable stops or limits for the operating variations in thedimensions of gaps a and b. The plates 5 and 5 may be held in threads ofcasing 2 so as to determine the base lines of gaps a and b with relationto theopposite faces of magnet 3. Further variations may be made byproviding for adjusting the pivot 4 of the magnet.

It will be clear that it is desirable to bias the forces of attractiontoward plate 5 in the preceding example. To accomplish this result, usemay also be made of the force of gravity by hanging the magnet in someother position than in the vertical as shown, or else a small spring maybe used to produce a similar eifect. The object of such bias is simplyto ensure the return of the magnet 3 to the starting position whenevercovers 5 and 6 are at the same temperature, while still permittingoperation as described when a temperature difference exists. In allcases it is desirable to limit the travel of magnet 3 to a small value,say a; inch'more or less, so that when operation takes place themagnetic attraction between the magnet and covers will not increase ordecrease excessively because of change in air gap dimension, and for thesame reason it may be desirable to keep the air gap relatively largecompared with magnet travel. I mention these things to indicate the manyways the simple structure may be varied for operation according to themain principles of the example given.

A useful feature of the Fig. 1 example is this. The pull across gap aand the opposite pull across gap b may differ by small amounts. Supposethe adjustments are made for them to differ by one came. The pull onmagnet 3 toward cover 5 might be an eleven ounce pull and toward plate 5a twelve ounce pull with the difierence one ounce. Then when plate 5 isheated causing a drop in its magnetic permeability, a drop of a littlemore than enough to decrease the magnetic force by one ounce will causethe switch operation. After operation has occurred the change inposition of magnet 3 will decrease gap b and thus increase theattraction across gap b slightly, holding the switch firmly in theoperated position. Likewise, the gap a is increased and attractionacross it decreased slightly, adding to the effect just mentioned. Theswitch is thus certain in operation and will not chatter or take up aposition between the contacts It and H. These relations andcircumstances give considerable and very useful operating scope for theswitch. I have operated it as a flame detector for oil burners. A crudemodel built to demonstrate the action operated on a temperaturedifference of degrees F. between cover 5 looking" at the flame and cover5 protected from the flame so as to be heated slower than cover 5. Itwill be appreciated that cover 5 exposed to receive the radiant heatfrom an oil burner flame will vary' 80- degrees F. without much delaybetween the time the flame goes on or goes off. This is only one use forsuch a switch but an important one to which I will refer in more detailbelow.

Another useful feature is seen in the fact that the switch device ofFig. 1 will operate at all temperatures. Consider the followingcircumstances. One example is to operate the switch automatically whenthere is a temperature difference of 80 degrees F. between covers 5 and6. Assume that cover 5 is at a temperature of several hundred degreesand cover 5 is at the same temperature. There will be no switchoperation.

Assume that starting that way the temperature aeranv of cover Iincreases about 80 degrees above that of cover 6. There will be a switchoperation. This is to say that with a high temperature existin in allparts of the switch device, and with the temperature of covers and 6 thesame, there is no switch operation even though the temperature changes.But when there is a differential change of the temperature, when cover 5becomes hotter than cover 6, or cover 8 becomes cooler than cover 5, inthe example by 80 degrees F. for instance, there will be a switchoperation. This feature may be stated by saying that changes in ambienttemperature do not cause the switch device to operate. This is becauseambient changes in temperature aflect the magnetic permeability ofcovers 5 and 6 equally andtheir opposite eflects on magnet 3 balance outleaving no operating effect. The relation of parts in this respectprovide for large scope of useful adjustments regardless of ambienttemperatures either high or low. The switch is useful for operations toindicate tendencies in high or low temperature operations.

The oil burner use diagrammatically indicated in Fig. 2 taken with theforegoing discussion shows all that one skilled in the art needs to putthe invention in such practice. The air tube 2| of a conventional oilpressure atomizing burner carries an oil pipe 22 to nozzle 23 beyondwhich the air-oil mixture is ignited and burned in the usual way. Aswitch embodying this invention has the purpose to turn off the burnermotor not shown, if the flame fails to start when it should or afterstarting fails to continue burning as it should. This is to say that theswitch device here is used as a flame detector for oil burners. Thereare various kinds of flame detector switching devices. The flamedetector is to move contact 25 over to contact 24 when the flame is wellstarted. If the flame goes out when it should stay on then contact 25 ismoved back to contact 26. The switch contact leads and circuits andgeneral burner operations are so well known that only the new parts ofthe switch operating device with relation to the burner flame will bespecifically described.

The indication of Fig. 2 is that the flam'e has just started. Itsradiant heat will immediately start to heat cover 21. This cover may beblackened on the outside and plated on the inside to get quicker heatingaction. Cover 29 may be plated on both sides if it is desirable to slowdown the rate of rise of its temperature. As cover 21 heats up itspermeability decreases. Attraction with magnet 30 is decreased whileattraction between cover 29 and magnet 30 at first remains substantiallyconstant. In a short time however covers 21 and 29 will both steadilyrise in temperature but at a difierent rate, that of cover 21 being at afaster rate until for example upon a temperature difference of about 80degrees F. between covers 21 and 29 will be established and then withthis differential in temperature of the two covers magnet 30 will besnapped over toward cover 29, being stopped short of hitting when switchcontacts 24 and 25 come together, see Fig. 3. These will be heldtogether by the slight increase in magnetic attraction between cover 29and magnet 30 resulting fronrthe change in position of magnet 30 to apoint closer to cover '29. When the flame goes out for any reason,covers 21 and 29 come to a uniform temperature. As they do this, magnet9|] moves back to its biased position because of the increasingattraction between cover 21 and magnet It resulting no air stream ispresent, and the two covers reach equaltem'perature more slowly. Thischaracteristic is made use of in some well known burner control circuitsto provide a delay between the time the burner stops and the time it maybe restarted, commonly termed the scavenging period. With the parts backin the indicated position, the device is ready for another cycle.

The 80 degrees F. temperature difference mentioned above is intendedonly as an example. The device may be adjusted to operate on othertemperature differences, and can be made more or less sensitive thanthis value. The temperature rise caused in the front cover by an oilburner flame depends chiefly on its distance from the flame. A rise of60 degrees in 10 seconds was noted in one instance with the detectorseveral inches behind the nozzle. The rise thereafter continued at adecreasing rate, with maximum rise about degrees in the front cover 21.In one example, with the detector several inches behind the nozzle, thefront cover rose 60 degrees in 10 seconds while the rear covertemperature did not rise at all in that short time. Then both coversincreased their temperatures together but the front one faster than therear cover. Thus the differential of temperatures between the two coverplates, at the end of 10 seconds was 60 degrees and since they bothcontinued to rise together but at different rates the diiierential oftemperatures was increased until it became an 80 degree difference. Thisdifierence in temperatures between the two plates caused the switch tooperate in the given example. If the device of that example were placedcloser to the nozzle of course the operatin differential would beestablished sooner than it was when the device was several inches backof the nozzle. If however it is for any reason desirable to keep thedevice in the more remote position from the nozzle or flame, a change inthe sensitivity could be made by adjustment as before described to makethe switch operate with a differential of 60 degrees between the twocover plates.

It will be seen that the parts of Fig. 2 are essentially like those ofFig. 1. The magnet may be of annular shape to pass oil pipe 22. Thecasing part 20 may have part 3| for support on the oil pipe. The magnet30 may be hung to swing more toward cover 21 than to cover 29 when thecover temperatures are the same. Contact 25 carried by an arm fastenedto magnet 30 and passing through an opening to clear cover 29 has acircuit lead passing out of casing 20. The general plan of the oilburner circuits provides that upon turning on the burner everythin willoperate with contacts 25 and 25 together but only for a predeterminedshort time. The burner will automatically shut down unless Within thattime contact 25 is moved over to meet contact 24. The flame detectorfunctions to move it over provided the flame is detected in operationand to move it back at any later time if the flame goes out so it cannot be detected. It could be put in other positions than on the oil pipeindicated. For example it could be put in as a smoke stack switch forthe heat of gases to heat cover 21 for its difference in efiect whenheated faster than cover 29.

Another use of the device is diagrammatically indicated in Fig. 4 as athermal time delay switch. In this case assume that contacts 33 and 34are to remain together until it is desired to move them apart after apredetermined time period. A heating coil 50 in a circuit operates toheat cover plate 36 when the circuit is closed. It will take apredetermined time to do this and meanwhile contacts 33-and 34 are inthe positions wanted. After such a time interval cover plate 39 pullsthe magnet 31 toward it and the contacts 33 and 34 are put in theirother relative positions. It will be noted that they will stay in thelatter positions until reset by hand. This may be done by a handoperated pivoted extension carrying the movable one of the contacts 33and 34. This hand operation will move the magnet back to be held byattraction with cover plate 36. The reason the contacts are notautomatically reset after the heat of coil 50 is turned off is that oncethe magnet is moved over to the opposite cover plate 39 it is closer tothat plate than to cover plate 36 and no bias spring, magneticunbalance, or other differential setting is present to cause itsautomatic return. In this it diflers from the imple form of warp orbi-metallic time delay switch. There are circumstances of use where itis desired that the return of the switch to original position afterautomatic operation be made by hand to make sure that attention iscalled to the heat event which caused the automatic switch operation.The way to do this as shown emphasizes when taken with the operations ofthe other examples the wide scope for application to various uses of mynew switch device.

Having disclosed my invention, I claim:

1. A heat-responsive switch, comprising, a permanent magnet having twoopposed polar faces, two armatures each constructed of magnetic materialhaving the characteristic that its permeability varies a material amountper degree of temperature change, means supporting said armatures spacedone from each of the polar faces of the magnet to provide a small airgap between each armature and the adjacent polar face of the magnet,means connecting said magnet and armature-supporting mean for relativemovement of the magnet back and forth between the two armatures, wherebythe magnet exerts forces in opposite directions on the two armatures andis held in one position between the plates when said armatures are ofequal temperature and whereby the magnet is movable relatively to thearmatures to another position when the temperatures of the armaturebecome unbalanced from unequal heating of the armatures, and a switchmember actuated by relative movement between the magnet and itsarmatures.

2. A heat-responsive switch, comprising, a permanent magnet having twoopposed polar faces, two armatures each constructed of magnetic materialhaving the characteristic that its permeability varies a material amountper degree of temperature change, means supporting said armatures spacedone from each of the polar faces of the magnet to provide a small airgap between each armature and the adjacent polar face of the magnet,means connecting said magnet and armature-supporting means for relativemovement of the magnet back and forth between the two armatures, wherebythe magnet exerts forces in opposite directions on the two armatures andis .held in one position between the plates when said armatures are ofequal temperature and whereby the magnet is movable relatively to thearmatures to another position when the temperatures of the armaturesbecome unbalanced from unequal heating of the armatures, and a switchcomprising a stationary contact and a contact carried by the magnet andmovable into and out of engagement with the fixed contact by themovement of the magnet relatively to the armature from one of saidpositions to the other, said contacts when engaged being held by a forceequal to the difference between the attractive forces of the magnet onthe two armatures.

3. A heat-responsive switch, comprising, a permanent magnet having twoopposed polar faces, two armature plates each constructed of magneticmaterial having the characteristic that its permeability varies amaterial amount per degree of temperature change, means supporting saidplates spaced one from each of the polar face of the magnet, said magnetbeing mounted on said means for movement back and forth between theplates, said magnet exerting forces in opposite directions on saidplates and assuming one position when the armatures are at equaltemperature and being movable to another position when one plate iheated to a substantially higher temperature than the other plate, and aswitch member actuated by the movement of said member from one of saidpositions to the other.

4. A heat-responsive switch, comprising, a tubular housing having asopposite end walls plates constructed of magnetic material having thecharacteristic that it permeability varies a material amount per degreeof temperature change, a permanent magnet pivotally supported from thehousing and located between the two plates, said magnet having twoopposed polar faces located one adjacent each plate, whereby the magnetexerts forces in opposite directions on the two plates, said magnetassuming one position between said plates when the latter are at equaltemperature and being movable to another position when one plate isheated to a temperature substantially higher than the other to changethe magnetic attraction between said one plate and the magnet, and aswitch member actuated by the movement of said magnet from one positionto another.

THEODORE J. MESH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 384,200 Ghegan June 5, 1888822,323 Thomson June 5, 1906 853,305 Kaisling May 14, 1907 1,433,462Kraker Oct. 24, 1922 1,499,112 Lippincott June 24, 1924 1,561,386 WhiteNov. 10, 1925 1,763,284 White June 10, 1930 2,185,490 Wittmann Jan. 2,1940 2,195,633 Rohr Apr. 2, 1940 2,207,871 Myers July 16, 1940 FOREIGNPATENTS Number Country Date 17,102 Switzerland July 8, 1898

